U.S. Pat. No. 4,093,450 to Doyle et al. describes a method for producing fine particle size cobalt metal powder by the hydrogen reduction of cobalt oxide obtained from a cobalt pentammine carbonate solution. The precipitate is formed by heating the solution to drive off ammonia and carbon dioxide to form a precipitate of cobalt oxide. This method requires a solution of approximately 4 grams per liter of cobalt to produce a size metal powder having a particle size less than one micron. Note that the final resulting particle size is highly dependent on the concentration of cobalt employed in the aqueous solution.
U.S. Pat. No. 2,879,137 to Bare et al. discloses the treatment of ammoniacal ammonium carbonate solution, obtained from leaching and/or containing nickel wherein the cobalt present in the cobaltic state is treated with an alkali metal or alkaline earth metal hydroxide under controlled temperature conditions to precipitate the nickel free of cobalt.
U.S. Pat. No. 3,928,530 to Bakker et al. discloses a method for the separation of nickel and cobalt by forming pentammine chloride complexes and solution containing a high concentration of ammonium chloride, and precipitating cobalt pentammine chloride.
In German Pat. No. 1,583,864, cobalt is recovered from scrap by digestion of the scrap in hydrochloric acid and magnesium chloride solution, followed by removal of iron and chromium impurities by precipitation at moderately acid pH followed by extracting a cobalt chloride complex with a long chain tertiary ammine in an aromatic solvent.
U.S. Pat. No. 4,108,640 to Wallis discloses a method for recovering metallic cobalt from an aqueous ammonical solution wherein the solution is contacted with a water immiscible liquid ion exchange reagent dissolved in an inert organic diluent to selectively extract the other metal from the solution and produce an organic extract loaded with the other metals and an aqueous cobalt bearing raffinate substantially free of the other metals.